Ring spinning machines or ring twister machines are provided with travelers running around on rings and acting as yarn guides, for inserting twists and for winding the yarn at proper tension onto the bobbin. Since these travelers are subjected to substantial stress, they wear out after a certain period and thus must be replaced. It is, however, not advisable to wait until individual travelers become defective because this leads to thread breakage and to nonuniform spinning.
Furthermore, replacement of individual travelers is not feasible since replaced travelers must be started with reduced running speed although the spindles of the associated set of travelers are commonly driven. Consequently, all travelers of one machine or one machine side must be replaced in common.
The time intervals within which a replacement has to be made depends on the speed of the spindles and on other factors and may amount to about three weeks. Once a replacement has been provided, the set of new travelers is run at reduced speed that is a half or a quarter of the normal operating speed and then are gradually, generally within a period of two or three hours, accelerated to the normal operating speed.
Up to now, the adjustment of the speed has been manually performed by increasing the speed of the driving motor at short time intervals--e.g. every quarter of an hour--by a certain magnitude until the normal operating speed of the travelers is obtained.
It is obvious that such a manual control requires continuous supervision and demands special attention from the operator. Nevertheless, experience has shown that even with such special attention, manual systems involve an uneven breaking or running in of the travelers.